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• I need a compact c/c++ code for motion vectors extraction from mp4 file without frame decoding [on hold]

  23 mars 2018, par Andyrey

  I have searched a lot of answers on this kind of question. Many of them point out to code, presuming frame decoding :

  DCT coefficient and motion vector extraction in encoded domain ;
  https://github.com/vadimkantorov/mpegflow ;
  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/extract_mvs.c.

  I implemented these codes in my program and saw they decode video frames, and then use frame side data for extracting motion vectors.

  Others give command lines for executing bynaries :

  Motion Vector extraction from encoded video file

  or just gives reference to huge set of library files with no idea what to do with them.

  What I badly need : code for extracting motion vectors from mp4 with no frame decoding (no pixel domain restoring). Is it possible ?

  From my 3rd reference I used code like next, where I suspect frame decoding happens :

  while (ret >= 0)
  
  {
  
      ret = avcodec_receive_frame(video_dec_ctx, frame);
  
     /*I omit some exclusion processing*/
  
      if (ret >= 0)
  
      {
  
          int i;
  
          AVFrameSideData *sd;
  
          video_frame_count++;
  
          sd = av_frame_get_side_data(frame, AV_FRAME_DATA_MOTION_VECTORS);
  
          if (sd)
  
          {
  
              const AVMotionVector *mvs = (const AVMotionVector *)sd->data;
  
              for (i = 0; i < sd->size / sizeof(*mvs); i++)
  
              {
  
                  const AVMotionVector *mv = &mvs[i];
  
                  printf("%d,%2d,%2d,%2d,%4d,%4d,%4d,%4d,0x%"PRIx64"\n",
  
                  video_frame_count, mv->source,
  
                  mv->w, mv->h, mv->src_x, mv->src_y,
  
                  mv->dst_x, mv->dst_y, mv->flags);
  
              }
  
          } 
  
          av_frame_unref(frame);
  
      }
  
  }

• Shell script works fine from shell but doesn’t work as expected when executed via PHP “shell_exec” code

  9 décembre 2019, par Eric Feillant

  This record.sh script shell is here and works fine on command line to record an MP4 file from a local flv live stream :

  DATE=`date +"%d-%m-%Y-%T"`
  
  if [ -s NAMESTREAM ]
  
  then
  
  cat config.php | dos2unix | grep auth | grep username | \
  
  awk -F ' ' '{print $3}' | sed "s/'//g" | sed "s/;//g" | while read VAR
  
  do echo $VAR > RECSTREAM
  
  echo "Starting recording ..."
  
  ffmpeg -i "rtmp://localhost/hls/$VAR" -crf 19 videos/"$VAR"_"$DATE".mp4
  
  done
  
  else
  
  echo "Streaming is not started, please start it before"
  
  fi

  I send a shell_exec to call the last shell script in a php script like this :

  $old_path = getcwd();
  
  chdir('/usr/local/nginx/html/mydir');
  
  $output = shell_exec('nohup ./record.sh >/dev/null 2>/dev/null &');
  
  chdir($old_path);

  The MP4 video files are generated but unreadable with VLC, etc… It seems that the problem is due to my PHP script but I am not able to know why.

  When executing from the shell command line : PHP myphpscript.php works fine, MP4 video files are OK. But from the PHP web page, the MP4 video files are corrupted.

  Any ideas ? Any param to test in FFmpeg to have a good mp4 video file ?

• How to code transcoding of TS to MP4 using ffmpeg

  28 juillet 2016, par CodeLearner

  ffmpeg -i testFile.ts -c:a aac -strict -2 -c:v copy testOutputFile.m4a

  The above command successfully converts testFile.ts(H264 video + Mpeg2 audio) to testOutputFile.m4a(H264 video + AAC audio).

  I need to implement the same functionality via code (using the ffmpeg library preferably ffmpeg v1.2).

  Does anybody know how to copy from one container(TS) to another(MP4) while encoding audio but not video ?